Worldwide, there are over one million children with HIV infection. 41At year-end 2000, the Thai Ministry of Public Health (MOPH) reported 20,052 and 2, 332 cases of children living with HIV and AIDS respectively, and 4,185 newly infected childrenC-The use of highly active antiretroviral therapy (HAART) has resulted in a significant reduction of morbidity and mortality among adults and children with HIV infection. 4344Nevertheless, few children have access to treatment and care for HIV disease, and less than 1% of children are on effective ARV therapy. Applicability of this study to both resource-rich and resource-limited settin.qs In resource-limited countries such as Thailand where ARV treatment for HIV-infected children according to international and national guidelines is not affordable, mechanisms for selecting groups of children to receive ARV treatment are needed. In resource-rich countries where the majority of children have access to care, the initiation of ARV therapy, if sooner than needed, can result in unnecessary morbidity. Once begun on ARV therapy, children are committed to life-long treatment. The use of ARV therapy can be associated with significant morbidity, namely toxicity and development of virological resistance. Lipodystrophy, dyslipidaemia and diabetes mellitus are examples of side effects that can result 45 4647 in poor health and quality of life. Lactic acidosis and mitochondrial toxicity are potentially life-threatening side effects 4649Successful treatment with ARV in children requires high-level compliance, which is not an easy task, and can be stressful for families and the children themselves.so As there is currently no cure for HIV infection, a balance between treating the disease and maintaining good health and quality of life must be weighed carefully. We believe that for both resource-rich and resource-limited settings, an evaluation of the appropriate time of initiation of ARV therapy is needed. The treatment strategy of deferred ARV therapy must be evaluated.